Title: Immunoassay Studies of Thyrotropin in Rat Pituitary Glands and Serum
Abstract: A sensitive and specific radioimmunoassay for rat thyrotropin (TSH) has been developed which utilizes 125I-mouse thyrotropic tumor TSH, antibovine TSH serum and USP bovine TSH as a standard. TSH in serum and pituitary homogenates was found in fractions corresponding to those previously shown to contain biological activity after gel filtration on Sephadex G-200. Serum TSH in normal rats after decapitation ranged from 15 to 66 μU/ml. During pentobarbital anesthesia, serum TSH was significantly lower (10–37 /μU/ml). Mean normal rat pituitary TSH content was 44 mU/gland. After 50μg thyroxine (T4) every other day for 14 days, serum TSH became undetectable (<6 μU/ml) in 5 of 7 rats, and pituitary content fell to 25 % of normal. Chronic propylthiouracil (PTU) treatment resulted in a progressive increase in serum TSH over a 12-week period. Pituitary TSH content, however, was below normal after 3 weeks of PTU, but rose progressively thereafter to exceed normal at 12 weeks. Following intravenous administration of thyroxine to PTU-treated rats, TSH fell exponentially with a mean ti of disappearance of 29 min. Twenty-four hr after T4, serum TSH fell to normal, while pituitary content increased 25% over control. These results show that pituitary TSH synthesis exceeds release after chronic thyroid hormone deprivation and that thyroxine administration acutely inhibits TSH synthesis as well as release. (Endocrinology81: 145, 1967)
Publication Year: 1967
Publication Date: 1967-07-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 36
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